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Publication Abstract from PubMed

Isoxazole is a five-membered heterocycle that is widely used in drug discovery endeavors. Here, we report the design, synthesis, and structural and biological characterization of SS-208, a novel HDAC6-selective inhibitor containing the isoxazole-3-hydroxamate moiety as a zinc-binding group as well as a hydrophobic linker. A crystal structure of the Danio rerio HDAC6/SS-208 complex reveals a bidentate coordination of the active-site zinc ion that differs from the preferred monodentate coordination observed for HDAC6 complexes with phenylhydroxamate-based inhibitors. While SS-208 has minimal effects on the viability of murine SM1 melanoma cells in vitro, it significantly reduced in vivo tumor growth in a murine SM1 syngeneic melanoma mouse model. These findings suggest that the antitumor activity of SS-208 is mainly mediated by immune-related antitumor activity as evidenced by the increased infiltration of CD8+ and NK+ T cells and the enhanced ratio of M1 and M2 macrophages in the tumor microenvironment.

Discovery of a New Isoxazole-3-hydroxamate-Based Histone Deacetylase 6 Inhibitor SS-208 with Antitumor Activity in Syngeneic Melanoma Mouse Models.,Shen S, Hadley M, Ustinova K, Pavlicek J, Knox T, Noonepalle S, Tavares MT, Zimprich CA, Zhang G, Robers MB, Barinka C, Kozikowski AP, Villagra A J Med Chem. 2019 Sep 26;62(18):8557-8577. doi: 10.1021/acs.jmedchem.9b00946. Epub, 2019 Sep 4. PMID:31414801^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.